Trends in male breast cancer in Spain, 1999-2023: a nationwide analysis of incidence and mortality.

[BACKGROUND] Male breast cancer (MBC) is rare and increasing globally, with limited data on trends in Spain. The study examines MBC trends, incidence, and mortality over a 25 year period (1999-2023) to guide public health strategies.

[METHODS] An ecological trend study was conducted using national mortality data from the Spanish National Statistics Institute and modeled incidence estimates from the Global Burden of Disease Study 2023. Age-standardized incidence and mortality rates (ASIR and ASMR) per 100,000 men were calculated using the European Standard Population 2013. Joinpoint regression identified temporal inflection points. Age-Period-Cohort (APC) modeling quantified age, period, and cohort effects for men aged 30-84 years.

[RESULTS] The study recorded 7594 MBC cases and 1,931 deaths. ASMR declined from 0.65 to 0.39 per 100,000 (AAPC - 1.8%), with significant declines from 1999-2006 (APC - 5.1%) and 2013-2023 (APC - 3.6%). ASIR remained largely stable (AAPC 0.1%), increasing slightly from 1999-2006 (APC + 1.7%) and declining thereafter (APC - 0.5%). The Mortality-to-Incidence Ratio decreased from 0.41 to 0.26. APC analysis demonstrated significant net declines in mortality (- 1.33%/year) and incidence (- 0.83%/year), primarily driven by period effects and lower risk among later birth cohorts. Mortality reductions were most pronounced among men aged 55-64 years.

[CONCLUSION] MBC mortality in Spain has declined steadily, reflecting improvements in clinical management, while stable incidence indicates minimal change in disease occurrence. Continued focus on early detection, male-specific awareness, and adherence to guideline-based therapy is essential to further reduce the MBC burden.